Service tax applicability on under construction properties

Good morning guys,

My client is buying a under construction property in Hyderabad from a notified builder for Rs 50 lakhs, my doubts are:

1. Service tax applicability - whether applicable on under construction property or not, if possible any section for reference.
2. Rate of service tax applicability - Whether it is to be charged at 4.5% (considering abatement) or at 15%.
3. Amount to be considered for computing service tax - Whether on Total sale value or Registered value?
4. Further the builder is demanding total service tax amount to be paid before registeration itself, but my doubt is it should be paid stage wise (Slab work, Brick work) etc..

Request fellow members to provide some clarification on the above issues, Thanks in advance.